Take-up devices for winding strand material comprising a traverse roller-bail assembly and a spindle assembly conventionally utilize a strand tension control means to compensate for any change in tension during winding. The tension control means normally rely on a spring or a plurality of springs to achieve the tension ranges desired. The tension level is adjustable within the range of operative spring extension. Take-up devices having spring tension controls are commercially available from the Leesona Corporation under, for example, Model No. 959.
The use of a spring as a tensioning device has two deficiencies. A first deficiency results from the fanning angle of the traversing means during winding onto a package. As shown in FIG. 1 of the present drawing, the fanning angle extends from position A at one end of the yarn package being wound to position B at the center of the yarn package to a position C at the other end of the yarn package, and then again back to B to A. This sequence is repeated throughout the winding operation. The fanning angle induces an up-and-down motion to a compensator arm as shown in FIG. 1B. Since the compensator is directly connected to the tension-inducing spring, this motion causes tension variation which, when plotted, is as shown in FIG. 1A.
A second deficiency in a tensioning device utilizing springs is that each spindle must be individually adjusted to set the tension. Not only is substantial time involved in making each adjustment, but human error in the adjustment invariably causes tension variation in an installation utilizing a plurality of take-up devices as such devices are commonly employed. Also, in some winding applications it is preferable to reduce the applied tension as the package grows in diameter to avoid bulging of the package. This, therefore, requires a means for adjusting the tension over the course of winding a strand package.
There are disclosures in the prior art which suggest using a fluid such as air to compensate for yarn tension change in a winding operation. Note, for example, Keith et al, U.S. Pat. Nos. 3,534,922 and 3,641,756, assigned to the predecessor of the assignee of the present application. In the devices disclosed in the '922 and '756 patents, a fluid material such as air provides a cushion supporting a strand loop during winding. As the strand tension increases or decreases, the loop becomes smaller or larger, respectively. As a result of the need for providing an air cushion, there is a substantial utilization of and loss of air; and, accordingly, the devices are expensive to operate.
Brouwer et al, U.S. Pat. Nos. 3,464,452 and 3,477,476, also assigned to the predecessor of the assignee of the present application, disclose strand storage devices wherein yarn is guided into a helical loop and pressurized fluid within the loop is directed outwardly against the strand. As tension in the strand decreases, the strand expands outwardly to form a larger loop; and, as tension in the strand increases, the strand contracts to form a smaller loop. The inventions of the '452 and '476 patents have deficiencies similar to the deficiencies of the Keith et al patents.
Accordingly, there is a need for a tensioning means not subjected to the deficiencies of a tensioning device made according to the prior art.